Treatment of hydrocarbons



June 30, 1942. 5, CQRSON Er AL 2,287,931

TREATMENT OF HYDROCARBONS Filed Def. '7. 1939 ARAFFINIC HYDROCARBONS DEHYDRO- GENATION AND DEHYDRO- CYCLIZATION ZONE PARAFFINS -e 1' I s SEPARATION ZONE g'1L t FRESH EXTRACTDN .I RECOVERED 9 sown-3w SEPARATION ZONE l4 AROMATICS AND OLEFINS ALKYLATION AND POLY- MERIZATION 'ZONE ARoMAflc's AND OLEFIN POLYMERS (0R WITH PARAFFINS) INVENTORS BEN B. CORSON GEORGE S. MONROE ATTORNEY Patented June 30, 1942 nai'regp 2,287,931 MEN'E or nr aoc wn B. (Carson and George S. Monroe, @hicago,

Hi... assignors to Universal Oil Products Company, Chicago, lit, a corporation of Delaware Appiication Gctober '2, 1939,8criai No. 298,390

(oi. i9652) 4 Claims.

This invention relates particularly to the conversion of relatively low-boiling normally liquid paramnic hydrocarbons into higher boiling hydrocarbons of improved octane number.

More specifically, it is concerned with a process involving the use of special catalysts and particular conditions of operation whereby relatively low boilin liquid parafllns can be converted eillciently into higher boiling oleflnic and aromatic hydrocarbons.

In one specific embodiment the present invention comprises a process for increasing the antiknock value andboiling range -of a relatively low boiling normally liquid paramnic hydrocarbon fraction which comprises contacting said fraction with a dehydrogenation and dehydrocyclization catalyst to produce a mixture of 'paramns, olefins and aromatics by reactions involving substantial dehydrogenation to olefins of parafins containing less than 6 carbon atoms in straight chain arrangement and dehydrocyclization to aromatics of parafilns containing 6 to 12 carbon atom in straight chain arrangement; extracting said mixture by a selective solvent to separate a product consistingloi olefins and aromatics from a paramnic raflinate; recycling said rallinate to further dehydrogenation and dehydrocyclization; recovering and recycling said solvent; and conducting said product consisting of olefins and aromatics to polymerization and allwlation treatment in the presence of, a precalcined composite of an acid of phosphorus and a substantially'inert adsorbent to form a product of high octane number containing relatively high proportions of olefin polymers and alkylated aromatics.

According to the present invention, parainnic hydrocarbons having less than 6 carbon atoms in straight chain arrangement are dehydrogenated largely to mono-olefinio hydrocarbons whilethose with a straight parafllnic chain of 6 to 12 carbon atoms are dehydrogenated in such a way that the chain of carbon atomsundergoes ring closure with the production in the simplest case of benzene from n-hexane and in the case of higher and the yields of desired alkylated aromatics decrease inproportion.

For the sake of illustrating and exemplifying lysts, the following structural equations are introduced:

cm on; CH;--4YHCH -CH; CHs4}=CH CH; n,

Isopentane Isopentene Hydrogen CH: CH CH, CH: CH OH 4 II 4H: 3: CH: E /CH v C I CH n-Hexanc v Benzene Hydrogen In the foregoing table the structural formula of n-hexane has been represented as a nearly closed ring instead of by the usual linear arrangement for the sake of indicatingthe possible mechanism involved. No attempt has been made to indicate the'possible intermediate existence of mono-olefins, di-olefins, hexamethylenes, or alkylated hexamethylenes, which might result from the loss of various amounts of hydrogen.

It is not known at the present, time whether ring closureoccurs at the loss of one hydrogen molecule or whether dehydrogenation of the chain occurs so that the first ring compound is an aromatic such as benzene or one of its derivatives.

While any suitable type of catalyst having dehydrogenating and cyclicizing properties may be employed for converting a relatively low-boiling normally liquid paramnic hydrocarbon fraction,

as one of natural gasoline boiling range, into substantial yields of oleflns-and aromatics, a satisfactory catalytic material comprises a major proportion of a refractory spacing agent, carrier, or support selected from the group consisting'of alumina, magnesia, silica and diatomaceous earth and relatively minor proportions of an oxide of a member of the left-hand columns of groups 4, 5 and 6 of the periodic table consisting of titanium, zirconium, cerium, hafnium, and thorium; vanadium, columbium and tantalum; chromium, molybdenum, tungsten and uranium.

The carriers or supports hereinabove referred to have relatively low catalytic activities, while the oxides of the elements mentioned are of relatively high catalytic activity and furnish by far the greater proportion of the observed catalytic effects. The oxides of these several elements vary somewhat in catalytic activity in any given reaction comprised within the scope of the invention and this variation may be greater in the case of different types of dehydrogenation and cyclization reactions.

Such dehydrogenation and cyclization catalysts are normally utilized at a temperature of the approximate order of 750-1200" F. under a pressure in the range of substantially atmospheric to approximately 100 pounds per square inch. Under these conditions approximately 25-30% dehydrogenation occurs per pass at a contact time in the approximate range of 0.1-2.5 seconds, although the contact time may occasionally be as high as approximately 50 seconds, depending upon the activity of the catalyst, the temperature of operation used and the composition of the material treated.

Dehydrocyclization of parafiins containing 6 to 12 carbon atoms in straight chain arrangement generally gives 20-50% conversion to aromatics per pass at a contact time within the approximate range of 01-50 seconds. which varies with the catalyst activity and the temperature of operation.

The resulting mixture of paraiiins, olefins and aromatics is preferably extracted by a selective solvent such as sulfur dioxide, furfural, nitrobenzene, phenol, cresol and B.B-dichloroethylether, for separation of a mixture of olefinic and aromatic hydrocarbons from unconverted paraflins which may be recycled to further dehydrogenation and cyclization treatment. The selective solvent employed is capable of being recovered by one of several well known methods including distillation where the extracted oil and solvent boil within different ranges and precipitation of the solvent by the addition of another material as water which renders the solvent and extracted oil mutually immiscible.

The mixture of aromatic and relatively low boiling oleflnic hydrocarbons so obtained by solvent extraction is then contacted with a granular phosphoric acid-containing composite under such conditions that alkylation of aromatics by olefins and polymerization of olefins will be moderate and a product.will be formed consisting of unconverted paraiiiins, alkylated aromatics, and polymers of the olefins formed by dehydrogenation of the paraflins having less than six carbon atoms in straight chain arrangement. Such alkylation and polymerization reactions may amounts of hydrocarbons with six or more carbon atoms in straight chain arrangement, dehydrogenates largely to olefins which polymerize to a higher boiling olefinic product of relatively high octane number.

For the purpose of illustrating the continuous process of the present invention the attached drawing shows diagrammatically a typical process flow for increasing the anti-knock value and boiling range of relatively low boiling parailln fractions.

Referring to the drawing a normally liquid paraffinic fraction is introduced through line I to dehydrogenation and dehydrocyclization zone 2, which may comprise a chamber or a plurality of chambers containing a granular dehydrogenation and cyclization catalyst maintained under conditions of temperature, pressure and time adequate to effect formation of olefinic and aromatic the granular catalyst.

generally 'be effected at a temperature of the order of 300-700 F. under some pressure in the range of substantially atmospheric to approximately 1000 pounds per square inch.

The granular phosphoric acid-containing composite preferred as catalyst for effecting alkylation of aromatics by olefins and polymerization of olefins comprises essentially a precalcined composite of an acid of phosphorus and a generally siliceous adsorbent such as diatomaceous'earth. This granular catalytic material and its method of preparation are described in United States Patent No. 1,993,513, and-others.

An original charge, such as a natural gasoline fraction. which contains a relatively high proportion of 6 to 12 carbon atoms straight chain hydrocarbons is preferably not converted completely in a single pass and the unconverted parafiins are recycled to further dehydrogenation and cyclicizing treatment so that a final product may be formed consisting mainly of aromatic and alkylated aromatic hydrocarbons. On the other hand,

a natural gasoline fraction containing only small The products from dehydrogenation and dehydrocyclization zone 2, comprising essentially hydrogen, olefins, aromatics, unconverted parafflns, and light hydrocarbon gases are conducted thence through line 3 to separation zone I from which light gases (C3 and less) are discharged through line 5.

From separation zone 4, normally liquid products consisting of olefins, aromatics and parafilns' are conducted through line 6 to extraction zone I in which a mixture of olefins and aromatic hydrocarbons may be separated from unconverted paraflins, said paraflins being conducted from extraction zone I through line 8 and recycled to further dehydrogenation and dehydrocyclization in zone 2. This extraction of a mixture of aromatic and oleflnic hydrocarbons from unconverted paraflinic hydrocarbons may be made either by batch or continuous processes, although from the standpoint of efliciency the method of counterflow extraction is preferable in commercial operations. The details of the batch and the counter-flow continuous procedures are generally well known in commercial practice and need not be enlarged upon here, since they form no special feature of the present invention.

Fresh solvent, as required, may be admitted to extraction zone I by way of line 9 while the solution containing dissolved oleflnic ,and aromatic hydrocarbons may be withdrawn through line Hi to separation zone I l in which the mixture of oleflnic and aromatic hydrocarbons is separated from the solvent, which is recovered and recycled through lines I! and 6 to further use in extraction zone I. If desired, a portion of the used and recovered solvent may be withdrawn from line l2 through branch line l3. The nature of separation zone I l is dependent upon the solvent used. For example, in case sulfur dioxide is the preferred solvent employed, it may be separated from the mixture of aromatic and oleiinic hydrocarbons by fractional distillation followed by washing of the hydrocarbon product with water and/ or alkali to remove dissolved traces of the solvent.

From separation zone II the mixture of oleflnic and aromatic-hydrocarbons is conducted through line I 4 to alkylation and polymerization zone l5, which may comprise a reactor or a plurality of reactors containing a granular precalcined composite of an acid of phosphorus and a generally siliceous adsorbent maintained at a temperature in the approximate range of 300-700" F. under some pressure in the range of substantially atmospheric to approximately 1000 pounds per square inch. In zone 15, aromatic hydrocarbons produced by dehydrocyclization reactions are alkylated ,by olefins resulting from dehydrogenation of certain constituents of the parafilnic fraction being processed. In case more oleiinic hydrocarbons are present than those utilizable in alkylating the simultaneously formed aromatics the remaining olefinic hydrocarbons polymerize in contact with the phosphoric acid-containing catalyst and produce higher boiling mono-olefinic material of relatively high octane number in admixture with the alkylated aromatics.

Aromatics. alkylated aromatics and olefin polymers present in alkylation' and polymerization zone 15 are conducted thence through line it. Alternatively, this product may be commingled in line It with a portion of the parafiinic ramnate separated from olefins and aromatics in extraction zone 7 and conducted thence through line 8. said parafinic rafiinate being conducted from line 8 to line it by way of alternative line H.

The following example is introduced to show results normally obtainable in the operation of the process, although these data are not presented with the intention of unduly limiting the broad scope of the invention:

Example A natural gasoline fraction consistlngof 3% n-butane, 57% pentanes. 22% hexane, 11% heptane and 7% octane and having an octane number of 73 was contacted with a granular material comprising 8% chromium sesquioxide on activated alumina at 1022" F. under atmospheric pressure using a liquid space velocity of 2.1 which corresponded to an average contact time of 1.7 seconds. n the basis of the fraction charged. the products from one pass over the catalyst consisted of 6.0% by volume of pentenes, 3.7% hexenes, and 14% aromatics together with 39.3% unconverted pentanes and 24.7% unconverted hexanes and higher boiling paraffins. Other conversion products were 3.8% condcnsible gas. 2.7% non-condensible gas (90% hydrogen), and

2.0% coke with 3.8% loss.

Extraction with liquid sulfur dioxide of the product formed by passing 100 parts by weight of the natural gasoline over the catalyst mentioned yielded an extract containing 14 parts by weight of aromatic hydrocarbons, 5.9 parts by weight of pentenes and 3.6 parts by weight of hexenes and a raifinate containing0.2 part by weight of pentenes and hexenes, 39.3 parts by weight of pentanes and 24.7 parts by weight of hexenes and higher boiling paramns. Contact of this olefinicaromatic hydrocarbon extract with a granular precalcined composite of pyrophosphoric acid and diatomaceous earth at 500 F. under 500 pounds pressure yielded a product consisting of aromatics, including alkylated aromatics and olefin polymers. Recycling of the unconverted paraifinic rafiinate which amounted to 64% by weight of the charge resulted in a 66% ultimate yield of a fraction with 85 octane number containing 88% aromatics and 12% of olefin polymers boiling in the range of decenes to dodecenes.

The character of the present invention and its novelty and utility can be seen from the preceding specification and numerical data presented,

although neither section is intended to unduly limit its generally broad scope.

We-claim as our invention:

1. A process for increasing the anti-knock value and boiling range of a paramnic hydrocarbon fraction containing hydrocarbons of less than 6 and hydrocarbons of at least 6 carbon atoms in straight chain arrangement, which comprises contacting said fraction with a dehydrogenation and dehydrocycliz'ation catalyst to produce a mixture containing parafilns, olefins and aromatics by reactions involving substantial dehydrogenation to olefins of parafiins containing less than 6 carbon atoms in straight chain arrangement and dehydrocyclization to aromatics of paramns containing at least 6 carbon atoms in straight chain arrangement, separating said mixture into a liquid phase and a gaseous phase and extracting the former by a selective solvent to separate olefins and aromatics from a parafiinic ramnate, recycling at least a portion of said railinate to further dehydrogenation and dehydrocyclization, and subjecting said olefins and aromatics to polymerization' and allrylation treatment in the absence of said gaseous phase and in the presence of a precalcined composite of an acidor phosphorus and a substantially inert adsorbent to form a product of high octane number containing relatively high proportions of olefin polymers and alkvlated aromatics.

2. A process. for increasing the anti-knock value and boiling range of a parac hydrocarbon fraction containing hydrocarbons of less than 6 and hydrocarbons of at least 6 carbon atoms in straight chain arrangement, which comprises contacting said fraction with a dehydrogenation and a dehydrocyclization catalyst to produce a mixture containing paramns, oleflns and aromatics by reactions involving substantial dehydrogenation to olefins oi paramns containing less than 6 carbon atoms in straight chain arrangement and dehydrocyclization to aromatics oi paramns containing at least 6 carbon atoms in straight chain arrangement, separating said mixture into a liquid phase and a gaseous phase and extracting the former by a selective solvent to separate olefins and aromatics from a parafllnic ramnate. subjecting said olefins and aromatics to polymerization and alkylation treatment in the absence of said gaseous phase and in the presence of a precalcined composite of an acid of phosphorus and a substantially inert adsorbent to form a product of high octane number containing relatively high proportions of olefin polymers and alkylated aromatics, and blending with said product at least a portion of said paraflinic ramnate.

3. A process for increasing the anti-knock value and boiling range of a parafiinic hydroto produce a mixture containing parafiins, oleflns and aromatics by reactions involving substantial dehydrogenation to olefins of paraihns containing less than 6 carbon atoms in straight chain arrangement and dehydrocyclization to aromatics of paramns containing at least 6 carbon atoms in straight chain arrangement, separating said mixture into a liquid phase and a gaseous phase and extracting-the former by a selective solvent to separate oleflns and aromatics from a paraffinic ramnate, recycling a'portion of said railnate to further dehydrogenation and dehydrocyclization, subjecting said oleflns and aromatics to polymerization and alkylation treatment in the absence of said gaseous phase and in the presence of a precalcined composite of an acid.

carbon iraction containing hydrocarbons of less than 6 and hydrocarbons of at least 6 carbon atoms in straight chain arrangement, which comprises contacting said fraction with a dehydrogenationand dehydrocyclization catalyst to produce a mixture containing parafflns, oleflns and aromatics by reactions involving substantial despams:

bydrogenatbmto olenns of paramns containing less than 6 carbon atoms in straight chain-arrangement and dehydrocyclization to aromatics oi paramns containing at least 6 carbon atoms in straight chain arrangement. separating said mix- .ture into a liquid phase and a gaseous phase and extracting the former by a selective solvent to separateoleflns and aromatics from a parafllnic raflinate, recycling at least a portion of said rafflnate to further dehydrogenation and dehydrocyclization, and subjecting said olefins and ammatics to polymerization and alkylation treatment in the absence of said gaseous phase and in the presence of a polymerizing and allwlating catalyst to form a product of high octane number containing olefin polymers and alkylated aromatics. v

BEN B. CORSON.

GEORGE S. MONROE. 

